#4 How Java Works

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n this lecture we will learn:
- Steps to execute the Java code
- What is Byte Code?
- Java is a platform-independent language
- Execution always starts from the main method
- Object-oriented language
- What are JRE and JDK?

#1
Steps to run the Java Code:-
- We required JVM to run a java code.
- The job of the JVM is to execute the java code that you have created but it does not accept the code directly.
- JVM does not accept the Java code as it only understands the Byte Code.
- Java compiler also known as javac is used to convert java code into byte code.
- The extension for the byte code is .class
- Thus, the code written by the programmer is first converted into byte code by the compiler and then that byte code goes to the JVM for further execution.
Programmer- Java Code- Compiler- Byte Code- JVM

#2
Java is a platform-independent language:-
It means you can run Java on any machine irrespective of any hardware or operating system.
The one thing that the machine requires to run a java code is a JVM.
:- JVM is platform dependent and it needs to be built for a particular OS.

#3
In Java, execution always starts from the main method:-
- JVM starts execution only with one first file. If you need to run multiple files you need to tell it which one is the first file through which JVM can start execution.
- The first file must contain the main method with its proper signature.
- In Java, execution always starts from the main method.
Signature of main method:
public static void main(String args[])

#4
Java is an object-oriented language:-
- Object-oriented means everything should be an object.
- We always required a class to create an object.

#5
JRE:-
- To run the Java application, you need extra libraries and need runtime. Runtime is something where you run things.
- You use extra libraries, and you also need an environment. An additional layer is present above the OS known as JRE.
- JVM is a part of JRE. JRE includes JVM and libraries.
JVM - Java Virutal Machine
JRE - Java Runtime Environment
- For development purposes, you need to install JDK (Java Development Kit) which consists of JRE and JVM.
- Java is WORA that is Write Once Run Anywhere provided that JVM and JDK installed.

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[aeroabrar_]

This is the explanation which every java developer needs, Kudos and Thank you sir.

[alessandrocupaiolo]

I work as Java developer since 2 years ago, and no one told me everything i watched in this video. Really thank you :)

[satyakanna]

This is the Marvelous Explanation sir Please provide Interview Questions Asked For Java Developers.

[balive]

Thanks for the great and clear explanation! I didn't know this about Java when I started learning it.

[gayathriyendru]

If I ever learned anything in the Java world it is because of you sir!! Thankful forever!!❤

[havory]

If VS Code gives you an error of the type "package system does not exist" make sure to have the "s" in "system" to be capital letter, alongside the first letter of string it also must be a capital letter.

[konradbartczak]

Cool content. I subscribed.
Up to java 8 we could only install JRE to run purpose.
But for java 9 everyone has to install the whole JDK.

[traveltribethings]

you explained this so beautifully! The most best part about your videos are unline others, you always try to give in depth knowledge on what happens in the backend which makes it more easier to learn.. I havent done coding in my entire life, but your videos are mind blowing!!! Keep explaining logic and concept wise..Great work!

[AbdoulayeZakaria-uy]

Wow, that's the type of instructors that all beginner in programming need

[SalakotPhilippines]

Thank you Navin Reddy my forever teacher since 2015

[_I_like_kebeb]

you are amazing, I have been learning Java for 1 year but now someone explained it correctly :D

[shariqsaiyed]

Literally, The way you explained !! I'm your fan!!

[BuiHoangucAnh-tnfz]

This is the explanation which every java developer needs, Thank you sir.

[chiltoncharles]

The explanation quality of this video is outstanding, thank you so much my brother, may god bless you

[NoahMichaelZ]

Hello, I'm From france and I'm learning java online and I found your channel when I first search for java videos. I watched all your java videos and thank you so much for these videos, I'm really grateful to you.

[faaizuddin]

Assalamualaikum sir, how you are ? I'm from Pakistani I watch your all video . Sir kindly upload advance java courses which based on industry requirements.

[sivaranjanis]

Great Navin. Very Useful . Thank you for such wonderful video

[brunomiguel]

Hi @Telusko, I hope you are doing well. First of all, thank you for this contents, however I have got confused when explained about the main method… when we use JSE we have a main method but in Jakarta we don’t have the main verb because is web application…

[robertjr]

This was the greatest explanation ever! Thank you!

[girlwhocodesandlifts]

Hi, is there any way I can see these things(JRE, JVM etc) in action? Any way to know what's happening at JRE/JVM level when I run a java program/application?